Field of the Invention
The present invention relates to a rotation angle detection device capable of detecting an abnormality in a resolver for detecting a rotation angle.
Description of the Related Art
A rotation angle detection device is used for detecting a rotation angle of a rotor driven by a motor, torque of a torsion bar in a power steering device of an automobile, and the like. In such rotation angle detection device, for example, a plurality of resolvers are mounted on a rotor, and the rotation angle of the rotor and the driving torque of the rotor are detected from the electrical angle of the resolvers.
For example, in a power steering device of an automobile, the steering angle of the steering wheel can be known through the detection of a difference in the rotation angle between both ends of a torsion bar rotationally operated by the steering wheel. However, in the rotation angle detection device using a plurality of resolvers, when an abnormality (such as a failure of the resolver, and a disconnection or a short-circuit of a wiring between the resolver and the rotation angle detection device) occurs in one of the resolvers, the rotation angle detection cannot be normally performed. Therefore, it is necessary to perform abnormality detection for each of the resolvers.
To cope with this, when a different DC bias voltage is applied, via a pull-up resistor, and the like, to each of two-phase output lines (a sine phase component output line and a cosine phase component output line) of respective different resolvers, it is possible to detect a disconnection of one of the two-phase output lines of the same resolver, a short-circuit between the two-phase output lines of the same resolver, and a short-circuit between the output lines of different phases of the different resolvers. However, when a short-circuit occurs between the output lines of the same phase of the different resolvers (the output lines having the same DC bias voltage), the bias voltage of the output lines is not changed, and hence the short-circuit cannot be detected.
To cope with this problem, Japanese Patent Laid-Open No. 2005-147733 discloses an abnormality detection device configured such that, on the basis of the fact that, when one of the electrical angles obtained from the signals of the same phase output line of each of different resolvers is set to correspond to the same mechanical rotational position of the rotor, the combinations of the electrical angles, each corresponding to a same signal level of the same phase output line of each of the different resolvers, are known beforehand, the combinations of the electrical angles are stored in a table, and the like, such that, when the signals of the same phase output line of the different resolvers coincide with each other, it is determined whether or not the combination of the electrical angles obtained from these signals is stored, and such that, when the combination of the electrical angles is not stored, it is determined that a short-circuit is caused between the same phase output lines of the different resolvers.
However, in the abnormality detection device, it is necessary that, in order to determine an abnormality in a plurality of resolvers, a plurality of cases of disconnection and short-circuit are discriminated by DC biasing the signal lines of the resolvers, and that, in order to determine the short-circuit between the same phase output lines that cannot be discriminated on the basis of the DC bias voltage, complicated combinations of the electrical angles in the normal state are stored in a table. This results in a problem that the abnormality determination processing is complicated and requires much processing time, so as to cause a decrease in the accuracy in the stored data and the rotation angle alignment between the resolvers. Further, this results in a problem that the circuit configuration becomes complicated so as to increase the number of components, the number of assembling steps, and the like, to thereby increase the manufacturing cost.
In order to solve the above-described problems, an object of the present invention is to provide a rotation angle detection device which has a simple circuit configuration, and which can quickly and highly accurately detect an abnormality of any one of a plurality of resolvers.